Interleukin-5 (IL-5 or IL5) is a lymphokine secreted by T cells and mast cells having biological activities on B cells and eosinophils. In murine hematopoiesis, IL-5 is a selective signal for the proliferation and differentiation of the eosinophilic lineage. See Yamaguchi et al., J. Exp. Med. 167: 43-56 (1988). In this respect, IL-5 function shows analogies with colony-stimulating factors for other myeloid lineages. Also, human (h) IL-5 is very potent in the activation of human eosinophils. See Lopez et al., J. Exp. Med. 167: 219-224 (1988) and Saito et al., Proc. Natl. Acad. Sci. USA 85: 2288-2292 (1988).
IL-5 mediates its activity through a cell membrane receptor-complex. This complex has been characterized physicochemically in both the murine and human system. Mouse pre-B cell lines depending on IL-5 for their growth have been developed from bone marrow and are used for IL-5 receptor analysis. See Rolink et al., J. Exp. Med. 169: 1693-1701 (1989). The human IL-5 receptor can be studied on a subclone of the promyelocytic cell line HL60 induced towards eosinophil differentiation. See Plaetinck et al., J. Exp. Med. 172: 683-691 (1990).
Eosinophilic differentiation is initiated using sodium butyrate. Only high affinity (Kd=30 pM) IL-5 binding sites can be found on these cells. However, cross-linking studies reveal the presence of two polypeptide chains involved in IL-5 binding, i. e., IL-5R-a and IL-5R-P chains. Devos et al., Canadian Patent Publication 2,058,003 describes a recombinant a chain of human IL-5R or parts thereof, DNA-sequences coding for such a receptor or parts thereof, and host cells transformed with such vectors. Takatsu et al., European Patent Publication 475,746 provides an isolated cDNA sequence coding for murine and human IL-5 receptor. The extracellular domain (ECD) of the human IL-5R-a chain can be expressed in cells, such as CHO cells, in a manner that allows for the enzymatic harvest of the receptor from the cell surface and its subsequent immobilization using a capture antibody (E. A. Whitehorn, et al., BiolTechnology 13: 1215 (1995).
A soluble human IL-5R-a chain can be used as an IL-5 antagonist in chronic asthma or other disease states with demonstrated eosinophilia. Eosinophils are white blood cells of the granulocytic lineage. Their normal function appears to be combating parasitic infections, particularly helminthis infections. However, their accumulation in tissues, a condition referred to as eosinophilia, is also associated with several disease states, most notably asthma. It is believed that the damage to the epithelial lining of the bronchial passages in severe asthmatic attacks is largely caused by the compounds released by degranulating eosinophils.
In U.S. Pat. No. 5,096,704, there is specifically disclosed the use of compounds which block the stimulatory effects of IL-5 in order to inhibit production and accumulation of eosinophils. The stimulatory effects of IL-5 were blocked by administering an effective amount of an antagonist to human interleukin-5, preferably using monoclonal antibodies or binding compositions derived therefrom by standard techniques. Monoclonal antibodies were selected by their ability to inhibit IL-5 induced effects in standard IL-5 bioassays, such as the ability to stimulate the growth and development of eosinophils in in vitro colony forming assays, and the ability to augment in vitro proliferation of the in vivo passaged BCL 1 lymphoma cells. The use of antibody fragments, e. g., Fab fragments, was also reported.
U.S. Pat. Nos. 5,668,110; 5,677,280; 5,654,276, and 5,683,983 also discuss peptides that bind the IL-5 receptors and block the effect of IL-5.
Currently glucocorticoid steroids are the most effective drugs for treating the acute effects of allergic diseases, such as asthma. However, the availability of alternative or complementary approaches to the treatment of disorders associated with eosinophilia would have important clinical utility.
Asthma has become the most common chronic disease in industrialized countries. Conventional methods and therapeutic agents may not be completely effective in the treatment of asthma or other immunomediated inflammatory diseases in all patient populations. Moreover, there remains a need for compounds that bind to or otherwise interact with the IL-5R, both for studies of the important biological activities mediated by this receptor and for treatment of disease. The present invention provides such compounds.